Conventional switching power supply systems sometimes operate in a so-called discontinuous operational mode. Operation of a conventional switching power supply in the discontinuous mode can include three-state switching operation period cycle.
For example, during a first switch state in the discontinuous mode switching cycle, the conventional power supply controller activates only a respective control switch to couple an inductor to a positive voltage source to increase an amount of current through the inductor to a load.
During a second switch state in the discontinuous mode switching cycle, the conventional power supply controller deactivates the control switch and activates a synchronous switch to couple the inductor to ground. In general, activating the synchronous switch decreases the current supplied through the inductor to the load.
During a third switch state in the discontinuous mode switching cycle, the conventional power supply controller deactivates both the control switch and the synchronous switch. While in the third switch state, generally no current flows through the inductor to the load. During the third switch state, an output capacitance of the power supply outputs current to power the load. Eventually, the voltage on the output capacitors falls below a threshold value at which time the conventional controller initiates activation of a new discontinuous mode switching cycle and activation of the control switch again (e.g., first switch state).
Thus, in general, operating a conventional power supply in the discontinuous mode reduces the switching frequency of the power supply and reduces an overall amount of current supplied through the one or more inductors to the load.
Operating the power supply in a continuous mode includes implementing only the first switch state and the second switch state.